The passage of Isaiah 13:9-16, like all Jewish oracles, deal with something the prophet saw in their past or were living through. Unfortunately people exposed to the theology of the Watchtower might still hold to the view that the writers were claiming to see the future.
The passage that Queequeg cites is not about God killing infants but about "Isaiah" writing a commentary on what happened to and around the nations of Israel and Judah during and after their exiles based on theology that, interestingly, all denominations of Judaism (including Orthodoxy) currently rejects.
The theology (which is likely that of Second or Third Isaiah) is that God punishes nations for their sins by bringing losses in wars upon them.
The words of Isaiah 13 describe what are supposed to be an eyewitness account lamenting the fall of Babylon after the manner of the fall of Nineveh. But the details are wrong. In fact it's "total destruction" descriptions are just poetic--as are likely the "infants" being "dashed to pieces" and the "wives being ravished" in verse 16 as the original invasion of the Persians was sudden and rather peaceful, and its was only during the Babylonian revolt that happened later wherein the Babylonians themselves took their own lives to keep from falling into the hands of the Persians (with some Babylonians strangling their own wives and children) that children died.